Field of the Invention
The invention relates generally to guiding catheters and, more particularly, to guiding catheters for use within branch arteries.
Background Information
Guiding or guide catheters are used as conduits to introduce therapeutic devices into smaller branch arteries or vessels within the human body. Guide catheters typically consist of a large bore, single lumen plastic extrusion. They usually have a low friction inner surface, such as a polytetrafluoroethylene (PTFE) liner, to facilitate movement of the therapeutic devices within the catheter. The guide catheters are offered in various diameters and have numerous pre-shaped curve styles available on their distal segments, to accommodate the various patient anatomies that are encountered. The catheters are constructed from relatively stiff materials, such that they remain as stable as possible while the therapeutic devices are passed through and manipulated.
In use, the catheters are introduced into a main artery or vessel within the body, such as the Aorta, and directed to the opening of a branch vessel, such as a coronary artery. The leading edge (distal end) of the guide catheter is seated at the opening (ostium) of the coronary artery while the rearward end (proximal end) of the guide catheter remains exposed outside of the patient, typically through the femoral, brachial, or radial artery. The guide catheter relies on the proper pre-shaped curve style and its inherent stiffness to remain stable at the coronary ostium. The guide catheter can then be used as a conduit to introduce, remove, and exchange various therapeutic medical devices, such as guidewires, PTCA catheters, and stents, into and out of the branch vessels for treatment of disease states.
In most cases, the therapeutic devices that are introduced into the branch vessel navigate and cross through very tortuous, tight and narrowed passages, such as those that occur with a coronary stenosis. While attempting to push the therapeutic device forward across difficult lesions associated with coronary stenosis, there is a reactive force created on the therapeutic device that becomes applied to the guide catheter, resulting in pushing the guide catheter away from the branch artery. Frequently this reactive force, also referred to as “push back,” overpowers the pre-formed distal curve shape as well as the stiffness of guide catheter, and causes the guide catheter to deflect and dislodge out of its seating in the ostium of the branch vessel. At this point, the therapeutic device can no longer be advanced forward as the guide catheter cannot provide the necessary support to the device. When this occurs, it necessitates re-seating of the guide catheter in the ostium or removal of all therapeutic devices, and the exchanging of the guide catheter to one with a more suitable curve shape.
A coaxial guide catheter extension has been developed to provide additional support to the guide wire. The extension extends beyond the parent guidewire down into the branch vessel, perhaps as much as 3 to 8 cm. This facilitates a method known as “deep seating,” which relies on the additional extension length within the branch vessel to create resistance against the vessel walls, and thereby enhance support to the guide catheter. While this method provides some additional support, the reactive forces on the extension during therapeutic device manipulations may result in deflection of the extension and/or deflection and dislodging of the guide catheter, and thus, loss of support to the therapeutic devices.
In addition, many times the obstruction within the branch vessel is located very near the ostium of the vessel, for example, 10 mm away or less. In these situations, the use of the known extensions for deep seating is not possible given the short distance available within the vessel in which to seat the extension. Furthermore, in order to be effective, the coaxial guidewire extension must be stiffer than the therapeutic devices passing through the extension, and the introduction of the stiffer catheter extension relatively deeply down into a branch artery can result in damage to the vessel and surrounding tissue.